Download Comparison of the mineral composition of leaves and infusions of

Page 1 of 7
Research Article
Comparison of the mineral composition of leaves and
infusions of traditional and herbal teas
Authors:
Jana Olivier1
Elize A. Symington2
Cornelia Z. Jonker1
Isaac T. Rampedi3
Tersia S. van Eeden2
Affiliations:
1
Department of
Environmental Sciences,
University of South Africa,
Roodepoort, South Africa
Department of Life and
Consumer Sciences,
University of South Africa,
Roodepoort, South Africa
2
Department of Geography,
Environmental Management
and Energy Studies,
University of Johannesburg,
Johannesburg, South Africa
Most research on teas has focused on organic composition and less attention has been given
to the mineral composition. The aim of this study was to examine and compare the mineral
compositions (Na, Mg, K, Ca, P, S, Fe, Mn, Zn, Cu and Al) of eight commonly consumed teas.
The teas included three traditional black or green teas (from Africa, China and Sri Lanka)
and five herbal teas – two from South America (maté and coca) and three from South Africa
(rooibos, honeybush and Athrixia phylicoides). Analyses were conducted on five samples of
dry tea leaves of each of the teas and their infusions (steeping time: 6 min) using identical
techniques in inductively coupled plasma optical emission spectrometry (ICP-OES). It was
found that each tea has a unique mineral profile. Dry tea leaves and their respective infusions
also exhibited different mineral profiles. The tea infusions that contained relatively higher
concentrations of beneficial minerals were maté, coca and Athrixia. High levels of aluminium
were found in the traditional black and green teas whilst rooibos was high in sodium. Although
teas are not rich sources of nutrients, the consumption of maté could contribute significantly to
dietary manganese requirements.
3
Correspondence to:
Jana Olivier
Email:
[email protected]
Postal address:
Private Bag X6, Florida 1710,
South Africa
Dates:
Received: 09 Feb. 2011
Accepted: 22 Aug. 2011
Published: 24 Jan. 2012
How to cite this article:
Olivier J, Symington EA,
Jonker CZ, Rampedi IT, Van
Eeden TS. Comparison of
the mineral composition
of leaves and infusions of
traditional and herbal teas.
S Afr J Sci. 2012;108(1/2),
Art. #623, 7 pages. http://
dx.doi.org/10.4102/sajs.
v108i1/2.623
© 2012. The Authors.
Licensee: AOSIS
OpenJournals. This work
is licensed under the
Creative Commons
Attribution License.
Introduction
Tea is the most commonly consumed beverage in the world after water.1 During 2004, tea
consumption reached three billion cups per day whilst 3.2 million tonnes of tea (Camellia sinensis)
were produced worldwide.2
Teas are exceptionally rich in polyphenolic compounds (flavonoid and phenolic acid), which
are potent antioxidants that scavenge free radicals and thereby protect the body from disease.3,4
Consequently, most of the research aimed at exploring the possible medicinal properties of herbal
teas has concentrated on their organic chemical constituents and the mechanisms by which
they produce medicinal effects. Considerably less research has been conducted on the mineral
composition of teas. Although literature is available on the mineral composition of individual
teas, comparative studies for the same minerals, using identical conditions and analytical
procedures, are rare. Moreover, it is not known whether the teas available to the South African
consumer have the same mineral composition as those in other countries where such research has
been undertaken.
Some minerals are essential for the functioning of the human body,5 with deficiencies (and in
some cases, excesses) causing serious diseases,6 whilst other minerals are harmful, even in small
quantities.4 In view of the growing consumption of teas, it is important to determine their mineral
composition in order to assess the possible health effects of tea on the consumer.
The aim of this study was to examine and compare the mineral compositions of eight teas (leaves
and infusions) originating from different parts of the world and to determine whether they
could contribute to the daily nutritional mineral requirements of consumers. The concentrations
of potentially harmful minerals in these teas also received attention. The teas were two brands
of traditional black tea (Camellia sinensis), one comprising a blend of teas from various African
countries and the other claiming to be pure Ceylon tea; green oriental tea (Camellia sinensis); maté
(Ilex paraguariensis) from Brazil; coca tea (Erythroxylum coca) from Peru; and three indigenous
South African herbal teas: rooibos (Aspalathus linearis), honeybush (Cyclopia intermedia) and
an as yet uncommercialised indigenous tea from the Limpopo Province, Athrixia phylicoides
(hereafter referred to as Athrixia). All, except maté and Athrixia, are readily available in South
African supermarkets. The mineral content of the dry tea material and the infusions produced
from them were analysed for 11 minerals, namely, sodium (Na), potassium (K), calcium (Ca),
magnesium (Mg), phosphorus (P), sulphur (S), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu)
and aluminium (Al) using identical analytical procedures.
http://www.sajs.co.za
S Afr J Sci 2012; 108(1/2)
Page 2 of 7
The teas
Research Article
antioxidants.29,30,31 Until a few years ago, rooibos tea was not
known of in the USA, but since 2005, sales of rooibos tea have
outstripped those of all other speciality teas in the USA.32
Traditional black and green teas
All traditional true teas derive from the leaves of the same
plant: Camellia sinensis (L.) Kuntze (Theaceae). Depending
on the processing method used, these teas are classified into
three major types: the non-fermented green tea, the semifermented oolong tea and fully fermented black tea. Lately
white, yellow, flavoured and scented teas have appeared on
the market.7
Although a number of scientific studies have indicated
that the consumption of black and green teas decreases the
risk of heart diseases, cancer, obesity, dental caries, bonerelated diseases, bacterial infections and the severity of
arthritis in humans and other animals,4,8,9,10,11,12,13,14 other
studies give contradictory results.4,15,16,17 Nevertheless, it is
widely accepted that the beneficial properties of these teas
are probably as a result of the antioxidant capabilities of the
polyphenolic compounds, the most important of which are
the flavonoid catechins3,4,17 and flavonols.18
According to Malik et al.19, a number of studies have reported
high levels of Al in traditional tea infusions. Because high
levels of Al have been associated with neurodegenerative
diseases such as Alzheimer’s and Parkinson’s,20 tea
consumption may be a cause for concern.
Yerba maté
Maté is a herbal tea derived from the dried leaves of a tree, Ilex
paraguariensis, that grows in Paraguay, Brazil and Argentina.21
Maté contains the antioxidants rutin and quercetin that have
chemopreventative properties.21 However, like black, green
and oolong tea, maté contains caffeine21 as well as tannins
and N-nitroso compounds.22 The latter two compounds may
be carcinogens. However, some conflicting results have
been reported,23,24 suggesting that other risk factors, such
as tobacco smoking, alcohol drinking and a high intake of
charcoal-grilled meat, are not only mutually correlated, but
also strongly associated with maté drinking.22 Maté has on
the other hand been labelled to have anticarcinogenic, antiinflammatory, cardioprotective, anti-obesity and cholesterol
lowering properties because of its antioxidant profile.21
Coca tea
Coca tea is a tisane (or herbal infusion) made from the
leaves of the coca plant (Eritroxilécea coca) – the same plant
from which cocaine and other alkaloids are obtained.25
After a chemical analysis of the tea, it was revealed that
the consumption of coca tea results in the ingestion of a
significant amount of cocaine and cocaine-related alkaloids.26
Although recent research has indicated that coca leaves
contain some nutrients, it was concluded that coca tea does
not have significant nutritional benefits.27
Honeybush (from various species of Cyclopia) is an
indigenous tea that has recently been introduced into the
local and international markets and is slowly gaining in
popularity.33 Research has confirmed that honeybush tea is
also rich in polyphenolic antioxidants.34
One of the most popular indigenous teas consumed by rural
communities living in the north-eastern part of South Africa
is brewed from the leaves and twigs of Athrixia phylicoides.
It is known locally as bush tea, daisy tea, Te a Thaba and itea
lentaba – the latter two meaning ‘tea from the mountain’ in
Sotho and Zulu, respectively. It has been used for centuries
as a tea and folk medicine and is thought to have commercial
development potential.28,35,36 Research into the chemical
and pharmacological properties of Athrixia is still in its
infancy, but has indicated that the tea is non-toxic, is rich in
antioxidants, has antimicrobial (antifungal and antibacterial)
properties and may contain a stimulant.37,38,39
The eight teas selected for the study thus represent a variety
of traditional teas from different geographical regions
(Africa, Sri Lanka and China) and herbal teas from South
America and South Africa. All eight teas are consumed in
high quantities that are thought to contribute to the health
status of the consumers.
Materials and methods
Materials
Five packets each of commercially available black, green,
coca, rooibos and honeybush teas were purchased from
supermarkets and health stores in Pretoria, South Africa. Two
kinds of black tea were purchased: one contained a blend of
tea grown in various African countries and the other was
purported to be pure Ceylon tea. Boxes of the commercial
teas were purchased from different stores. The boxes of black,
green, coca and rooibos teas contained tea infusion bags,
which each contained about 2.5 g of tea. Some of the boxes
of honeybush and maté teas consisted of tea bags and others
of loose-leaf plant material. One of the boxes of maté tea was
purchased in Brazil; the others were purchased from a local
store in Pretoria. Dry Athrixia leaves and small twigs were
harvested from the Haenertsburg and the Sekhukhuneland
regions of the Limpopo Province in South Africa during
2007, 2008 and 2009 and dried in accordance with traditional
tea preparation methods.35,36 The South African Biodiversity
Institute (SANBI) in Pretoria verified the plant material as
being Athrixia phylicoides.
All chemical analyses were conducted at the Agricultural
Research Council (ARC) Institute for Soil, Climate and Water
laboratory in Pretoria.
Mineral analysis of dry tea material
South African herbal teas
Rooibos tea is brewed from the stems of Aspalathus linearis.
Research has indicated that this tea is rich in phenolic
28
http://www.sajs.co.za
Weights for mineral analysis were standardised at 1 g of
dry leaf material. Samples were taken from each of the five
S Afr J Sci 2012; 108(1/2)
http://www.sajs.co.za
86
555
598
14
14
61
139
555
904
244
11 337
1326
5631
478
321
302
471
675
3284
2581
319
3830c
10 676e
Athrixia (S. Africa)
908a
1886a
Honeybush (S. Africa)
162
323
1704b
1792a
Rooibos (S. Africa)
3478c
10 556e
Coca (S. America)
455
656
6196d
Maté (S. America)
4972d
214
1956
937
5252
Green (Oriental)
s.d., standard deviation; S. America, South America; S. Africa, South Africa.
Means within columns with the same letter do not differ significantly at p < 0.05.
1176
105
922ab
184
532a
169
680a
642
3750d
72
1190b
1876
14 662c 1473
626
3658a
806
2762a
10 550b 1142
811
13 448c
1600
13 896
414
2534
397
5499
229.0abcd 73.2
23.9
91.6a
24
117.6ab
81.5
370.6d
236.7
375.0d
73.3
312.6
73.7
142
476.1
13.4
111.6a
7.9
31.6a
8.5
56.5a
6.9
67.0a
1521.4c 443.1
196.3
939.2
562.5
33.1
9.7
32.4bc
2.4
14.1a
6.1
20.2ab
2.3
23.9ab
23.2
66.3d
8.9
40.4
7.7
18.1
13.5
0.2
9.4b
1.4
4.0a
1.0
4.8a
0.8
11.5bc
6.0
14.5c
3.6
23.0
8.46
1874
150
1720c
158
752a
45
874a
120
2330d
130
1210b
477
2892
191
826
671
46
302a
350
1076b
293
2797c
85
232a
2
75a
45
132
77
210a
a
f
2582de
2.1
28.4e
d
c
41.2c
16.9
244.0a
b
cd
188.0abc
456
17 267d
c
c
2492c
82
c
b
1888b
199
4076b
Black (Ceylon)
S Afr J Sci 2012; 108(1/2)
Average
s.d.
144
246a
70a
82a
337a
448a
1362c
901b
1268c
99
319a
101
2630ef
0.4
11.7bc
4.3
26.5ab
376.6
837.8b
48.6
264.6bcd
17 250d 1235
398
2906c
103
1914b
353
Aluminium
Mean
s.d.
Mean
Sodium
s.d.
Mean
Sulphur
s.d.
Copper
s.d.
Mean
Zinc
s.d.
Manganese
Mean
s.d.
Mean
Iron
s.d.
Mean
Potassium
s.d.
Mean
Phosphorus
s.d.
Magnesium
Mean
4616bc
Perusal of the mineral composition data presented in Tables
1 and 2 reveals that each tea contained the full set of eleven
minerals. However, the amount of a specific mineral differed
from one tea to another, displaying a unique mineral profile
for each tea. It is also clear that the dry tea leaves and
corresponding infusions exhibited different mineral profiles.
Black (Africa)
Mineral composition
Mean
Results and discussion
s.d.
Means and standard deviations were calculated for each
of the minerals. Several one-way analyses of variance
(ANOVAs) were performed using Statistical Package for
the Social Sciences40 to calculate whether there were any
differences amongst the mean concentrations of each of
the identified minerals for the different samples of teas. If
significant differences on the ANOVA F-statistics (based
on the mean sum of squares) at the p < 0.05 level (or lower)
were observed, a Duncan’s post-hoc test was conducted to
determine which tea samples differed from the others.
Calcium
All eight teas were prepared using a ratio of 1 g per
100 mL boiling water and infused for 6 min (to ensure
standardisation). Infusions were prepared by adding 2 g
of dry tea material to 200 mL boiling deionised water. The
resulting infusion was stirred with a glass rod for about 30 s
to ensure proper wetting, covered and steeped for a total of
6 min. The steeped infusion was then immediately decanted
through a fine stainless steel sieve to remove contact with
the tea leaves and allowed to cool. Thereafter, the cooled
solution was filtered and analysed using the procedure
outlined above.
Tea
Mineral analysis of infusion liquid
TABLE 1: Concentrations (mg/kg) of minerals in the dry tea leaves of eight traditional and herbal teas from different geographical regions.
Samples (1 g) were digested with 7 mL HNO3 (65% AR nitric
acid) and 3 mL HClO4 (70% perchloric acid) at temperatures
up to 200 °C and brought to volume in a 100-mL volumetric
flask. An aliquot of the digest was used for the inductively
coupled plasma optical emission spectrometry (ICP-OES)
determination of Ca, Mg, P, K, Na, Fe, Zn, Mn, Al and Cu.
Each element was measured at an appropriate emission
wavelength, chosen for high sensitivity and lack of spectral
interference. The wavelengths used were 383.826 nm for
Mg, 422.673 nm and 317.933 nm for Ca, 213.618 nm for
P, 769.896 nm for K, 589.592 nm for Na, 259.94 nm for Fe,
257.61 nm for Mn, 213.856 nm for Zn, 324.754 nm for Cu
and 396.152 nm (confirmed 308.215 for digests) for Al. The
instrument (Varian-Liberty 100 ICP-OES spectrometer, Varian
Inc., Palo Alto, CA, USA) was calibrated against a series of
standard solutions containing the elements of interest in the
proportions found in typical leaf samples. Sulphur was also
determined by ICP-OES using a wavelength of 181.978 nm
employing a JY Horiba Ultima (after being purged with
nitrogen to prevent interference from atmospheric oxygen).
sources of each of the eight teas for analysis (i.e. a total of 40
samples). Analyses were replicated thrice to ensure accuracy.
Where applicable the tea leaves were removed from the tea
bags. Samples of all teas were ground prior to analysis to
approximate the same size distribution of plant material.
495
Research Article
Mean
Page 3 of 7
2.1
212.6
157.5
1.0
1.8
1.3
11.2
s.d., standard deviation; S. America, South America; S. Africa, South Africa.
Infusions were prepared in a ratio of 1 g tea to 100 mL water with a steeping time of 6 min.
Means within columns with the same letter do not differ significantly at p < 0.05
772
Average
102
1505d
Athrixia (S. Africa)
145
492b
Honeybush (S. Africa)
37
331ab
Rooibos (S. Africa)
185
Coca (S. America)
276
1247c
1699d
Maté (S. America)
20
Green (Oriental)
149
233a
406ab
Black (Ceylon)
163
265a
Black (Africa)
S Afr J Sci 2012; 108(1/2)
591
1400
60
1006b
162
436a
205
608ab
811
524
2599c
3984d
56
59
725ab
838ab
157
1007b
1219
1053
32
305a
166
353a
167
337a
472
111
706b
3158e
112
126
958bc
1088c
192
1519d
922
10 910
505
12 017c
784
3135a
850
2559a
185
9595b
13 341d 1745
690
168
17 182e
13 650d
977
16 834e
5388
5.8
0.2
4.9ab
1.3
4.4ab
2.0
7.6cd
1.6
1.6
9.0d
6.4bc
2.6
1.0
3.8a
6.5bc
1.2
3.5a
2.4
181.4
0.9
16.7a
3.2
9.4a
3.9
14.5a
224.6
4.0
28.9a
781.0c
41.0
5.9
73.2a
230.6b
147.8
297.2b
266.6
12.7
1.5
5.9ab
1.1
3.4a
2.2
5.4ab
1.2
12.6
33.4d
10.9bc
1.7
4.8
15.7c
15.1c
2.6
12.1bc
10.1
4.7
0.3
1.7a
0.1
0.4a
0.2
0.9a
0.9
1.8
6.9c
7.0c
2.5
0.7
8.7d
6.6bc
1.4
5.1b
3.2
990
130
966b
118
163a
98
368a
516
90
479a
1365bc
443
402
1543c
1636c
307
1388bc
632
539
19
101a
371
919b
408
2610c
21
42
88a
132a
53
17
93a
108a
103
175a
868
5.0a
1.2a
4.5a
8.2a
66.9a
60.5
s.d.
160.4
351.6b
344.4b
478.4b
Mean
Aluminium
s.d.
Mean
Sodium
s.d.
Mean
Sulphur
s.d.
Copper
Zinc
s.d.
Mean
Manganese
Iron
s.d.
Mean
Potassium
s.d.
Mean
Phosphorus
s.d.
Magnesium
Mean
Mean
s.d.
Mean
s.d.
http://www.sajs.co.za
s.d.
These mineral profiles of the infusions are generally in
agreement with previous research19,43 indicating that the
concentrations of a number of minerals in traditional black
and green teas far exceeded those in South African herbal
teas. A comparison of results with those by Malik et al.19
showed that our values were lower across the board, except
for Al. These lower values could be expected because Malik
et al. infused their tea leaves for 15 min, whilst our steeping
time was only 6 min.
Calcium
Comparison of the profiles of minerals in the infusions of
all eight teas (Table 2) reveals that black teas provided the
richest sources of all minerals; in terms of high concentrations
of individual minerals, maté and coca teas were superior to
all the other teas. Excluding Al, black tea from Sri Lanka
(Ceylon) surpassed tea made from a blend of African teas
as a source of minerals, and Athrixia was a richer source of
minerals than the other South African herbal teas.
Tea
The variation in mineral profiles between the tea leaves
may be as a result of a number of factors, the most likely
being differences in the soil type, climate,42 altitude,
cultivation procedures such as fertiliser application, and
genetic differences between the different plant species. It is
notable that rooibos and honeybush, both indigenous to the
Cape and which grow in sandy soils, had similar mineral
profiles. Rooibos, which grows only on the West Coast, was
exceptionally rich in Na. Conversely, Athrixia, which grows
in dolomitic areas, contained relatively large amounts of Ca
and Mg.
TABLE 2: Concentrations (mg/kg) of minerals in residues of infusions of eight traditional and herbal teas from different geographical regions.
These results are largely consistent with those obtained by
Malik et al.19 for Ca, Mg, Fe, Mn and Zn. However, Malik
et al. found considerably lower amounts of Al in black and
green teas than were found in the present study. It should be
noted that the results for Al obtained in this study agree with
those of Jansen et al.41 who indicated that Camelia sinensis are
Al accumulators and concentrations exceeding 1000 mg/kg
have been found in their leaves.
Mean
Comparison of the mineral profiles (Table 1) of the eight dry
tea leaf samples reveals that Athrixia, black and coca teas had
the highest total mineral content. Maté and coca teas had the
largest variety of minerals in appreciable amounts, followed
by black and green teas. The herbal teas, rooibos and
especially honeybush, had significantly lower amounts of
all minerals (except sodium in rooibos). The Camellia sinensis
teas were the richest sources of K, Cu, S and Al, whilst maté
tea leaves were exceptionally rich in Mg, Mn, Fe and Zn. The
highest concentrations of Ca were in Athrixia and coca leaves.
Coca tea leaves were also rich in P and Fe.
According to our results presented in Table 1, five of the six
major minerals (K, Ca, Mg, P and S) are the most abundantly
occurring minerals in the dry tea leaves. The infusions
exhibited the same general pattern except that relatively less
Ca than Mg, P and S was present (Table 2). Three of the trace
minerals – Zn, Cu and Fe – were the elements present in the
lowest concentrations in both leaves and infusions.
246.3
Research Article
Mean
Page 4 of 7
Page 5 of 7
Research Article
TABLE 3: Mean mineral content (mg/250 mL) of the residue of infusions of eight traditional and herbal teas from different geographical regions.
Tea
Potassium
Iron
Manganese
Zinc
Copper
Sulphur
Sodium
Aluminium
Black (Africa)
Calcium
0.66
Magnesium Phosphorus
2.52
3.80
42.09
0.01
0.74
0.03
0.01
3.47
0.44
1.25
Black (Ceylon)
0.58
2.10
2.72
42.96
0.01
0.18
0.04
0.02
4.09
0.23
0.86
Green (Oriental)
1.02
1.81
2.40
34.13
0.02
0.58
0.04
0.02
3.86
0.27
0.88
Maté (S. America)
3.12
9.96
1.77
33.35
0.02
1.95
0.08
0.02
1.20
0.22
0.17
Coca (S. America)
4.25
6.51
7.9
23.99
0.02
0.07
0.03
0.02
3.36
0.33
0.02
Rooibos (S. Africa)
0.83
1.52
0.84
6.40
0.02
0.04
0.01
0.00
0.92
6.52
0.01
Honeybush (S. Africa)
1.23
1.09
0.88
7.84
0.01
0.02
0.01
0.00
0.51
2.30
0.00
Athrixia (S. Africa)
3.76
2.52
0.76
30.04
0.01
0.04
0.01
0.00
2.42
0.25
0.01
s.d., standard deviation; S. America, South America; S. Africa, South Africa.
The steeping time for infusions was 6 min.
TABLE 4: Dietary reference intakes of men and women (19–50 years old) for
selected minerals.
Mineral
Dietary reference intake
Men
Calcium (mg/d)
Magnesium (mg/d)
Women
1000†
1000†
400–420‡
310–320‡
Phosphorus (mg/d)
700‡
700‡
Potassium (mg/d)
4700†
4700†
Iron (mg/d)
8‡
18‡
Manganese (mg/d)
2.3†
1.8†
Zinc (mg/d)
11‡
8‡
Copper (μg/d)
900‡
900‡
Sulphur
Sodium (mg/d)
Aluminium
ND
ND
1500†
1500†
–
–
Source: National Academy of Sciences50
ND, not determinable because of lack of data of adverse effects in this age group and
concern with regard to lack of ability to handle excess amounts. Source of intake should be
food only to prevent high levels of intake.
†, recommended daily allowance.
‡, adequate intake.
Dietary value
From a nutritional perspective, tea is regarded as fluid intake
that generally does not contribute to mineral requirements.
Tea, especially black and rooibos, is regularly consumed by
South Africans as a beverage.44
In order to determine to what extent tea consumption might
supply dietary minerals, the amount of available minerals
for each cup of tea was calculated. These amounts were
derived from Table 2 using a conversion factor of 1 mg/kg
= 0.0025 mg/cup, assuming that 1 g tea leaves are used per
100 mL boiling water at household level, and that 1 cup holds
250 mL liquid (Table 3).
The nutritional attributes of tea consumption can be assessed
by comparing the values in Table 3 with the dietary reference
intakes (DRIs) given in Table 4.
It is evident that teas contain minute amounts of minerals,
and therefore they do not make a significant contribution
to meeting mineral requirements. The exception is maté tea
which provides about 1.95 mg Mn per 250 mL (Table 3).
This concentration is the required daily Mn intake for adult
women (Table 4). Men would have to consume at least one
and a half cups of maté tea per day to meet their DRI for
Mn. The positive contribution that maté tea could make as
a dietary source of Mn has also been noted by others.19,45
Although green and black teas from Africa also contain
http://www.sajs.co.za
considerable amounts of Mn, consumption of three to four
cups would be required to meet the daily Mn requirement.
Even though the K levels are higher than any of the other
minerals in all of the teas, one cup of tea still provides less
than 1% of the DRI for adults. In this study, none of the other
infusions could be considered as rich sources of the major
and trace minerals.
The low concentrations of potentially harmful minerals in
teas can be considered to be advantageous. Sodium is present
in very low concentrations in all eight teas. Even rooibos, with
the highest Na content, could not be considered to constitute
a health risk. Concerns have also been expressed about the
intake of Al in food,46 as well as in traditional teas.45,46,47 The
World Health Organization (WHO)48 limits the Al content
in drinking water to 200 μg/L (i.e. 0.2 mg/L or 0.05 mg/
cup49) and, in 2007, the WHO48 established a provisional
tolerable weekly intake for food of 1 mg Al/kg body mass.
The Al concentrations of 1.25 mg/cup of black tea and
0.9 mg/cup of green tea should be taken note of by people
with low body mass who consume numerous cups of tea per
day. The excessive consumption of black and green tea by
young children should be discouraged.
Conclusion
We have reported on the mineral content of three traditional
black and green teas and five herbal teas from different
geographical regions. Traditional teas all derive from the
plant Camellia sinensis, whilst the herbal teas included maté
and coca teas from South America, and rooibos, honeybush
and Athrixia tea from South Africa. All eight teas are
consumed in relatively high quantities and are believed to
have health-promoting properties.
Chemical analyses were conducted to determine the
concentration of eleven minerals: Ca, Mg, K, Na, P, S, Mn,
Zn, Fe, Cu and Al, in dry tea leaves as well as in tea infusions,
using ICP-OES. Although the recommended infusion times
vary between 30 s to 10 min or more for different infusions
and, traditionally, some of these teas are boiled, a standard
infusion time of 6 min was used in this study for two reasons.
Firstly, to ensure standardisation of results and, secondly, to
determine mineral intake levels of the common consumer
who rarely has time to boil the infusions or infuse ‘teas’ for
more than a few minutes before consumption. It should,
S Afr J Sci 2012; 108(1/2)
Page 6 of 7
however, be noted that differences in infusion time may well
affect the bioavailability of minerals.
We found that all teas contained the full complement of
eleven minerals, but in minute quantities when compared
to the daily mineral requirement. The exception was the
concentration of Mn in maté tea – one to one-and-a-half cups
of maté tea per day could supply the recommended intake of
Mn. Our study thus confirms previous findings21 indicating
that, in general, teas cannot be considered as a major source
of dietary nutrients. Nevertheless, even the small amounts of
minerals present in teas would supplement those nutrients
consumed in food.
Paradoxically, the low concentrations of some minerals may
be advantageous. Al is present in very low concentrations in
the speciality teas but its higher content in black and green
teas should be noted.
A comparison of the mineral content of the eight teas revealed
that maté and coca teas were superior to the others. Although
Camellia sinensis teas have higher values of K, Cu and S than
the other teas, their relatively high Al content detracts from
their postulated health effects. Rooibos and honeybush
have considerably lower concentrations of most minerals
when compared to the other teas. Of the three South African
indigenous herbal teas, Athrixia is the most mineral rich. In
terms of their mineral profiles, the consumption of herbal
teas such as maté, coca, rooibos, honeybush and Athrixia teas
are a good choice for health-conscious consumers.
Acknowledgements
We thank the University of South Africa and the National
Research Foundation of South Africa for financial support
(GUN: 2048685); Lynne Meyer and Leslie Adriaanse for
editorial assistance; Jackie Viljoen and Unisa Language
Services for editing the manuscript and Christel Troskiede Bruin for critical reading. We also especially thank
Nina van Vliet and Mike Phillpott (ARC-ISCW), not only
for developing the analysis methods, but also for their
constructive comments and suggestions on the manuscript.
Competing interests
We declare that we have no financial or personal relationships
which may have inappropriately influenced us in writing
this article.
Authors’ contributions
J. Olivier was the project leader and principal researcher. C.Z.
Jonker, I.T. Rampedi, T.S. van Eeden and E.A. Symington
made significant conceptual contributions to the research
and wrote parts of the article.
References
1. Wu CD, Wei G. Tea as a functional food for oral health. Nutr Oral Health.
2002;18(5):443–444.
http://www.sajs.co.za
Research Article
2. Hicks A. Review of global tea production and the impact on industry of the
Asian economic situation. Bangkok: Food and Agricultural Organization
Regional Office for Asia and the Pacific; no date.
3. Hertog MGL, Feskens EJM, Hollman PCH, et al. Dietary anti–oxidant
flavonoids and risk of coronary heart disease: The Zutphen Elderly
Study. Lancet. 1993;342:1007–1011. http://dx.doi.org/10.1016/01406736(93)92876-U
4. Yang CS, Wang ZY. Tea and cancer: A review. J Natl Cancer Inst.
1993;58:1038–1049. http://dx.doi.org/10.1093/jnci/85.13.1038
5. Lukaski HC, Penland JG. Functional changes appropriate for determining
mineral element requirements. J Nutr. 1996;126:2354S–2364S. PMid:8811798
6. Viteri FE, Gonzalez H. Adverse outcomes of poor micronutrient status in
childhood and adolescence. Nutri Rev. 2002;60(suppl):S77–S83. http://
dx.doi.org/10.1301/00296640260130795
7. Hicks A. Current status and future development of global tea production
and tea products. Au J T. 2009;12(4):251-264.
8. Cabrera C, Artacho R, Giménez R. Beneficial effects of green tea – A review.
J Am Coll Nutr. 2006;25(2):79–99. PMid:16582024
9. Katiyar SK, Mukhtar H. Tea in chemoprevention of cancer: Epidemiologic
and experimental studies (review). Int J Oncol. 1996;8:221–238.
PMid:21544351
10. Geleijnse JM, Launer LJ, Hofman A, et al. Tea flavonoids may protect against
atherosclerosis: The Rotterdam Study. Arch Inter Med. 1999;159:2170–2174.
http://dx.doi.org/10.1001/archinte.159.18.2170, PMid:10527294
11. Han LK, Takaku T, Li J, et al. Anti–obesity action of oolong tea. Int J
Obes Relat Metab Disord. 1999;23:98–105. http://dx.doi.org/10.1038/
sj.ijo.0800766, PMid:10094584
12. Weisburger JH. Tea and health: The underlying mechanisms. Proc Soc Exp
Biol Med. 1999;220:271–275. http://dx.doi.org/10.1046/j.1525-1373.1999.
d01-46.x, PMid:10202402
13. Hegarty VM, May HM, Khaw KT. Tea drinking and bone mineral density
in older women. Am J Clin Nutr. 2000;71:1003–1007. PMid:10731510
14. Sarkar S, Sett P, Chowdhury T, Ganguly DK. Effect of black tea on teeth. J
Indian Soc Pedod Prev Dent. 2000;18:139–140. PMid:11601182
15. Blot WJ, McLaughlin JK, Chow W-H. Cancer rates among drinkers
of black tea. Crit Rev Food Sci Nutr. 1997;37:739–760. http://dx.doi.
org/10.1080/10408399709527800, PMid:9447273
16. Mukamal KJ, MacDermott RN, Vinson JA, et al. A 6-month randomized
pilot study of black tea and cardiovascular risk factors. Am Heart J.
2007;154:724.e1–724.e6.
17. Gardner EJ, Ruxton CHS, Leeds AR. Black tea – Helpful or harmful? A
review of the evidence. Eur J Clin Nutr. 2007;61(1):3–18. http://dx.doi.
org/10.1038/sj.ejcn.1602489, PMid:16855537
18. Higdon J, Drake VJ, Dashwood RH. Tea [homepage on the Internet].
c2008 [cited 2008 Feb 13]. Available from: http://lpi.oregonstate.edu/
infocenter/phytochemicals/tea
19. Malik J, Szakova J, Drabek O, et al. Determination of certain micro and
macroelements in plant stimulants and their infusions. Food Chem.
2008;111:520–525. http://dx.doi.org/10.1016/j.foodchem.2008.04.009
20. Krewski D, Yokel RA, Nieboer E, et al. Human health risk assessment
for aluminium, aluminium oxide, and aluminium hydroxide. J Toxicol
Environ Health B Crit Rev. 2007;10(Suppl 1):1–269. http://dx.doi.
org/10.1080/10937400701597766, PMid:18085482, PMCid:2782734
21. Heck CI, De Mejia EG. Yerba mate tea (Ilex paraquariensis): A comprehensive
review on chemistry, health implications, and technological considerations.
J Food Sci. 2007;72(9):R138–R151. http://dx.doi.org/10.1111/j.17503841.2007.00535.x, PMid:18034743
22. Goldenberg D. Maté: A risk factor for oral and oropharyngeal cancer. Oral
Oncol. 2002;38:646–649. http://dx.doi.org/10.1016/S1368-8375(01)00127-0
23. Bates MN, Hopenhayn C, Rey OA, Moore LE. Bladder cancer and mate
consumption in Argentina: A case-control study. Cancer Lett. 2007;246:268–
273. http://dx.doi.org/10.1016/j.canlet.2006.03.005, PMid:16616809
24. De Mejia EG, Song YS, Ramirez-Mares MV, Kobayashi H. Effect of
yerba mate (Ilex paraquariensis) tea on topoisomerase inhibition and oral
carcinoma cell proliferation. J Agric Food Chem. 2005;53(6):1966–1973.
25. Encyclopedia: Coca [homepage on the Internet]. c2008 [cited 2008 Feb 26].
Available from: http://www.nationmaster.com/encyclopedia/Coca
26. Jenkins AJ, Llosa T, Montoya I, Cone EJ. Identification and quantification
of alkaloids in coca tea. Forensic Sci Int. 1996;77(3):179–189. http://dx.doi.
org/10.1016/0379-0738(95)01860-3
27. Penny ME, Zavaleta A, Lemay M, et al. Can coca leaves contribute to
improving the nutritional status of the Andean population? Food Nutr
Bull. 2009;30(3):205–216. PMid:19927600
28. Van Wyk B-E, Gericke N. People’s plants. Pretoria: BRIZA, 1997; p. 99–100.
29. Joubert E, Ferreira D. Antioxidants of rooibos tea – A possible explanation
of its health promoting properties. S Afr J Food Sci Nutr. 1996;8(3):79–83.
30. Von Gadow A, Joubert E, Hansmann CF. Comparison of the antioxidant
activity of aspalathin with that of other phenols of rooibos tea (Aspalathus
linearis), alpha-tocopherol, BHT and BHA. J Agric Food Chem. 1997;45:632–
638. http://dx.doi.org/10.1021/jf960281n
31. Marnewick JL, Joubert E, Swart P, et al. Modulation of hepatic drug
metabolising enzymes and oxidative status by unique South African herbal
teas, rooibos (Aspalathus linearis) and honeybush (Cyclopia intermedia), green
and black (Camellia sinensis) teas in rats. J Agric Food Chem. 2003;51:8113–
8119. http://dx.doi.org/10.1021/jf0344643, PMid:14690405
S Afr J Sci 2012; 108(1/2)
Page 7 of 7
Research Article
32. Simrany J. The state of the US tea industry. Tea Association of the United
States [homepage on the Internet]. c2005 [cited 2007 Nov 16]. Available
from: www.teausa.com
42. Fraga CG. Relevance, essentiality and toxicity of trace elements in human
health. Mol Aspects Med. 2005;26:235–244. http://dx.doi.org/10.1016/j.
mam.2005.07.013, PMid:16125765
33. Du Toit J, Joubert E, Britz TJ. Honeybush tea – A rediscovered South
African herbal tea. J Sustainable Agric. 1998;12:67–84.
43. Street R, Szakova J, Drabek O, Mladkova L. The status of micronutrients
(Cu, Fe, Mn, Zn) in tea and tea infusions in selected samples imported to
the Czech Republic. Czech J Food Sci. 2006;24(2):62–71.
34. Kamara BI, Brand J, Brandt EV, Joubert E. Phenolic metabolites from
honeybush tea (Cyclopia subternata). J Agric Food Chem. 2004;52:5391–5395.
http://dx.doi.org/10.1021/jf040097z, PMid:15315375
35. Olivier J, De Jager A. [An ethnobotanical survey of an indigenous South
African tea: Athrixia phylicoides]. Suid-Afrikaanse Tydskr Natuurwetenskap
Tegnol. 2005;24(4):139–147. Afrikaans.
36. Rampedi IT, Olivier J. The use and commercial development potential of
Athrixia phylicoides: A multipurpose indigenous South African plant. Acta
Acad. 2005;37(3):165–183.
37. Mashimbye MJ, Mudau FN, Soundy P, Van Ree T. A new flavonol from
Athrixia phylicoides (bush tea). S Afr J Chem. 2006;59:1–2.
38. Joubert E, Gelderblom WCA, Louw A, De Beer D. South African herbal
teas: Aspalathus linearis, Cyclopia spp. and Athrixia phylicoides – A review. J
Ethnopharmacol. 2008;119:376–412.
39. McGaw LJ, Steenkamp V, Eloff JN. Evaluation of Athrixia (bush tea)
for cytotoxicity, antioxidant activity, caffeine content and presence of
pyrrholizidine alkaloids. J Ethnopharmacol. 2007;110(1):16–22. http://
dx.doi.org/10.1016/j.jep.2006.08.029, PMid:17045437
40. Statistical Package for the Social Sciences. Version 17.0. Chicago, IL: SPSS
Inc.; 2008.
41. Jansen S, Watanabe T, Dessein S, et al. A comparative study of metal levels
in leaves of some Al-accumulating Rubiaceae. Ann Bot. 2003;91(6):657–663.
http://dx.doi.org/10.1093/aob/mcg071, PMid:12714364
http://www.sajs.co.za
44. Department of Health, South African Government. The National Food
Consumption Survey (NFCS): Children aged 1-9 years, South Africa, 1999
[homepage on the Internet]. c2000 [cited 2008 Feb 05]. Available from:
http://www.sahealthinfo.org/nutrition/food7tables7-28.pdf
45. Wróbel K, Wróbel K, Urbina EM. Determination of total aluminium,
chromium, copper, iron, manganese, and nickel and their fractions
leached to the infusions of black tea, green tea, Hibiscus sabdariffa, and Ilex
paraguariensis (mate) by ETA-AAS. Biol Trace Elem Res. 2000;78(1–3):271–
280. http://dx.doi.org/10.1385/BTER:78:1-3:271
46. Bamji NMS, Kaladhar M. Risk of increase aluminium burden in the
Indian population: Contribution from aluminium cookware. Food Chem.
2000;70:57–61. http://dx.doi.org/10.1016/S0308-8146(00)00068-6
47. Mehra A, Baker CL. Leaching and bioavailability of aluminium, copper
and manganese from tea (Camellia sinensis). Food Chem. 2007;100(4):1456–
1463. http://dx.doi.org/10.1016/j.foodchem.2005.11.038
48. World Health Organisation (WHO). Sixty-seventh report of the joint FAO/
WHO expert committee on food additives. Evaluation of certain food
additives and contaminants. WHO Technical Report Series 940. Geneva:
WHO; 2007.
49. Mamba BB, Rietveld LC, Verberk JQJC. SA drinking water standards
under the microscope. Water Wheel. 2008;7(1):25–27.
50. National Academy of Sciences [homepage on the Internet]. c2008 [cited
2008 Feb 05]. Available from: www.iom.edu/
S Afr J Sci 2012; 108(1/2)